The present invention relates to ophthalmic flat roughing wheels which are used to grind the edges of glass and plastic lenses and a method of making a wheel of the present invention.
It is common practice in the optical industry to mold or fabricate plastic or glass lenses to oversized dimensions and then grind the edges of the lenses to a particular shape and size to properly fit a particular frame. The lenses are first rough ground with a flat roughing wheel and then fine ground and beveled with a beveling or finishing wheel. A beveled edge is generally required to secure the lens to the frame. A conventional flat roughing wheel has a grinding surface layer which is made of uniformly distributed diamond particles in a metallic matrix and which is wide enough to accommodate lenses of various widths and diopters as is encountered in commercial use. The use of a conventional flat roughing wheel to grind lenses of various widths and diopters results in a "hollowed out" area in the center of the grinding surface where most wear is experienced. For continued use, such a wheel must be "re-trued" to present a flat grinding surface by grinding down the high edges of the grinding layer. It would be desirable, however, if a roughing wheel could be made which would remain flat for a longer period of use and which would be easier to re-true. And in accordance with the present invention, it has been discovered that this can be uniquely accomplished.
Heretofore it has been known to make abrasive wheels for various uses having sections of varying degrees of wear resistance and composition although it has remained for the present inventor to discover the particular ophthalmic flat roughing wheel of the present invention as well as a method of making the wheel and its use. Examples of patents teaching abrasive disks having layered or varying make-up include U.S. Pat. No. 3,203,774, Aug. 31, 1965 to Pratt for "Method of Making an Abrasive Cut-Off Disk"; U.S. Pat. No. 1,986,849, Jan. 8, 1935 to Pohl et al. for "Abrading Material and Process for Preparing the Same"; U.S. Pat. No. 2,084,513, June 22, 1937 to Tone for "Abrasive Article"; U.S. Pat. No. 2,027,132, Jan. 7, 1936 to Webster for "Grinding Wheel"; U.S. Pat. No. 1,403,416, Jan. 10, 1922 to Katzenstein for "Abrasive Wheel for Form Grinding"; U.S. Pat. No. 226,066, Mar. 30, 1880 to Hart for "Emery Wheel"; U.S. Pat. No. 440,682, Nov. 18, 1890 to Wood for "Burr Remover"; U.S. Pat. No. 3,049,843, Aug. 21, 1962 to Christiansen for "Abrasive Cutting Devices"; U.S. Pat. No. 2,600,815, June 17, 1952 to Turner for "Apparatus for Rough and Fine Grinding of Spherical Surfaces"; and U.S. Pat. No. 1,399,400, Dec. 6, 1921 to Pellow for "Lens Grinder".
Wherefore, it is an object of this invention to provide a new and improved ophthalmic grinding or roughing wheel and a new method of making same. It is a further object of this invention to provide an ophthalmic roughing wheel which can be used longer than a conventional wheel but is economical to manufacture. Yet another object of the present invention is to provide a new type of roughing wheel which is easier and more economical to "re-true" than conventional wheels.